Robertas Zavalis

Flexural capacity and stiffness of monolithic biaxial hollow slabs

The article presents a research on flexural behaviour of hollow monolithic reinforced concrete slabs. It focuses on the results of experimental investigation into full-size hollow reinforced concrete slabs and analyses their flexural capacity and stiffness. The self-weight of the slabs directly depends on the shape and number of hollows. An increase in the hollowness of a slab significantly reduces the load caused by self-weight. This allows increasing the estimated length of the slab under the same payload. An increase in the amount of hollows of the slab changes the stiffness of the slab cross-section that has a direct impact on slab deflection. Considering the shape of the slab cross-section, theoretical calculations of the flexural capacity and deflection of experimental slabs were made. The design of a new type of slabs and variations in different parameters of the slab experience difficulties in conducting a large amount of experimental tests. Therefore, the initial analysis may apply to numerical simulation. The paper describes the principles of designing a numerical model. The calculations were made using DIANA software. The stiffness and flexural capacity of the hollow slabs were established employing numerical simulation compared to the results of experimental investigations. The findings indicate that numerical simulation can be applied for analysing the stress state of the examined structures.

Numerical and experimental analysis of grouted hollow block masonry under compression

Abstract Highly hollow masonry units, which allow reducing the weight of masonry constructions and improving heat and sound insulation qualities, are commonly used in masonry construction. Filling the hollows with concrete, or concrete with light additives, results in complex masonry. Overall performance of such masonry is affected by initial stresses, which are caused by shrinkage deformations of different infill concrete and masonry units. Behaviour of infill concrete and concrete blocks is analysed by applying numerical detailed micro modelling. Experiments revealed that masonry deformations of blocks with concrete filled hollows are similar to those of longitudinal deformations of infill concrete samples. σ-e relations were received through numerical micro modelling and compressive strength of masonry match values were estimated during experiments.

Aukštos temperatūros įtakos betono ir armatūros savybėms bei jų bendrai elgsenai analizė

Santrauka Nagrinėjama gelžbetonio ir jo komponentų (betono ir armatūros) elgsena aukstoje temperatūroje, tiriamos betono stiprumo ir deformatyvumo savybės kintant temperatūrai. Atliekama teorinių ir eksperimento būdu gautų rezultatų lyginamoji analizė. Aptariami pagrindiniai atsparumo ugniai skaiciavimo principai. Pasinaudojus baigtinių elementų metodo programa COSMOS/M, suskaiciuoti gelžbetoninio elemento skerspjūvio temperatūros pasiskirstymo laukai pagal standartinio gaisro kreive. Pagal gautus temperatūrinius laukus zonų metodu nustatyta teorinių ir eksperimento rezultatų skirtumo įtaka elemento laikomajai galiai.

Investigation of the Behavior of Hardening Masonry Exposed to Variable Stresses

This paper analyzes the behavior of masonry under variable loads during execution (construction stage). It specifies the creep coefficient for calcium silicate brick masonry, presenting the research data of masonry deformation under variable and constant long-term loads. The interaction of separate layers of composite material in masonry is introduced and the formulae for determining long-term deformations are offered. The research results of masonry’s compressive strength and deformation properties under variable and constant long-term loads are presented. These are then compared to calculated ones. According to the presented comparison, the calculated long-term deformations coincide quite well with those determined experimentally.